1. Field of the Invention
This invention pertains to a system for ejecting droplets of liquid on command suitable for use in apparatus such as ink jet printers and facsimile recorders.
2. Description of the Prior Art
This invention is an improvement on the system described in U.S. Pat. No. 3,683,212, issued to Steven I. Zoltan on Aug. 8, 1972, and assigned to the same assignee as the present invention.
A system constructed as described in the Zoltan patent having the dimensions cited by way of example works very well when the pulse rate is less than about one kH. If the pulsing is continuous and the pulse rate is gradually increased above about one kH, alternate increases and decreases in droplet velocity may be observed.
When a burst of pulses equally spaced in time is applied to the system, and the time interval between pulses exceeds about one millisecond, the resulting droplets are ejected with uniform spacing. However, when the time between pulses is decreased to a fraction of a millisecond, the first several droplets which are ejected generally have irregular spacing.
The above described irregularities are undesirable in many applications. An experimental and theoretical investigation has shown that they are caused by acoustic resonances, reflections, and interference phenomena in the liquid in the system.